Nothing wrong, IMHO, with taking some profits after a big run-up. (It's surprising how many people are content to just "let it ride" instead of buying low and selling high. I'm not advocating market timing, but if your portfolio is way, way up, and you can "lock in" the next year to several years of expenses and convert that to cash without materially impacting your AA, then by all means - I'd do that every single time).
It's possible (though unlikely, IMHO, with Schiller PE at all time highs, inverted yield curve, etc) that I'd miss "some" additional upside IN THE SHORT TERM, but more than likely, I or anyone else taking a "sell high" approach now is going to be ahead in the long term, as those $$s are now locked and not subject to gut-wrenching drops which are increasingly likely to be on the near horizon. Would that likely recover in 3, 5, 10 or more years? Probably. But the "bird in hand" approach definitely does have merit if it pays the bills and allows you to keep a still reasonable portion of the long-term bucket invested at the same time..
A prudent ER plan IMHO incorporates good use of cash and knowing when to replenish the cash bucket. It does seem that there's an over-reliance at times on being mostly fully invested, and I've always found that to be somewhat surprising. My own plan strategically uses cash more than most, and moves reasonably sized chunks in and out of equities when it makes sense - ie: if I can fund next year's expenses by selling a highly appreciated fund or equity that's had a very strong recent run, that'd be a time I'd consider it. (In fact, I'm planning to do that as soon as it's more advantageous from a tax standpoint [ie: early next Jan for 2020 taxes] on a stock I own that's almost tripled since I bought it). That might vary my AA but as long as it stays within a general range, I'm good with it and the increased SWAN factor that approach brings..
